The availability of unlimited solar energy, in the form of solar radiation and heat, is an attractive source of energy for many purposes. Many applications for harnessing or using solar radiation to generate electricity or a useful mechanical output exist. For example, silicon solar cells which respond to light from the sun are used to generate electricity, which then may be used directly or stored by charging a battery. Typically, solar cells generate only small amounts of electricity; so that solar cell systems generally are used to operate electronic devices requiring relatively low power levels.
Solar cell arrays many square feet in size have been used to power direct current motors to operate pool pumps and the like. Typically, however, solar cell arrays need to be extremely large in order to produce any substantial quantity of electricity. As a result, such solar cell arrays have not been found to be a practical source for utilizing energy from the sun, in all but a few specialized cases.
Another approach to harnessing the energy of the sun is to focus the solar radiation through a lens system onto a contained boiler to generate steam. The steam then may be utilized to turn a rotor, which operates an electric generator.
Systems have been developed for utilizing solar energy in a closed loop sealed system to generate electric power. One such system is disclosed in the Parker U.S. Pat. No. 4,945,731. The Parker patent discloses a heat cycle engine in the form of a hollow cylindrical container enclosing a working fluid in the form of a radiant energy absorber. A window is disposed in the first end of the container to receive solar energy, which is concentrated on the window from a parabolic reflector. The working fluid is heated in the area behind the window, and then travels toward the opposite end of the container to operate a turbine. The cooled fluid then returns back to the end adjacent the window on a continuous basis. The turbine located within the container is coupled through a magnetic coupling to an external shaft, which may be used to drive an electric generator. The system of this patent uses specialized working fluid selected from halogens and interhalogens; and the system is relatively complex and expensive to manufacture.
Another type of closed loop, hermetically sealed solar power generator is disclosed in the patent to Smith U.S. Pat. No. 4,391,100. The Smith patent discloses a closed loop, sealed, recirculatory water solar powered generator which has a hollow globular water boiler with a focusing lens in it. Solar energy is reflected onto the lens from a parabolic mirror; and the heat then is focused on the water inside the boiler. Steam is generated and is obtained from the top of the boiler to drive a steam turbine. The water then passes through a condenser to a reservoir, from which it returns back to the boiler. The boiler and the steam turbine are separate parts in this system; but the system of Smith is of more simple construction than the system of the Parker patent and uses a readily available, inexpensive working fluid in the form of water.
Another system of the same general type as the one disclosed in the Smith patent is disclosed in the patent to Lane U.S. Pat. No. 4,213,303. This patent is directed to a sun tracking, solar energy boiler using a lens system to heat a small tube of water to create steam. The steam then is used to drive a turbine, the shaft of which is coupled to an electric generator to produce useful output energy. The condensed steam then is supplied back to a condenser and reservoir, from which it is supplied again to the boiler tube.
A different system for converting solar energy to low cost mechanical or electrical power is disclosed in the Abbot U.S. Pat. No. 3,654,759. The Abbot patent divides a reflected solar input beam into a plurality of concentrated cones of solar radiation through the use of a Fresnel lens array. Each of these cones of concentrated radiation then is focused on a relatively thin black box to heat air contained within the box. When a suitable pressure is built up within a box, the heated air is passed outwardly through a valve and to a nozzle directed to a turbine to rotate the turbine. The different boxes are opened and closed at different times to admit air into the boxes, and then to release the pressurized heated air from the boxes in a timed sequence to continuously apply jets of heated air to different portions of the rotor to rotate it. The mechanical motion of the rotor then is used to produce electrical energy.
The foregoing systems of the prior art all include various disadvantages. The Abbot system is not a closed system, and therefore is subject to variations in the supply of ambient air used in the system. Clearly, the greater the temperature differential between the air entering into the boxes and that to which the air is heated by the lens system, the greater the power output from the Abbot system. Therefore, it is desirable to separate, to as great a degree as possible, the output nozzles used to drive the turbine from the location of the input air to the boxes. The other patents, which have been discussed above, all are relatively complex in the number of components and in the array of lenses and specialized boilers which must be incorporated.
It is desirable to provide a solar powered steam turbine generator which is efficient in operation, which overcomes the disadvantages of the prior art, and which is simple and inexpensive to manufacture.